1. Field of the Invention
The invention relates to a quick change cutting cylinder arrangement for letter envelope and hygiene machines, where the cutting cylinder is bolted to a left and a right bearing unit in a form-locking manner.
In paper converting and hygiene machines, i.e. machines which produce articles such as sanitary napkins, disposable diapers, handkerchiefs, table napkins, etc., it is often necessary to change certain cylinders, particularly those cylinders which depend on format when that format is changed. In this connection, it is necessary, on the one hand, that each cylinder run exactly true by reason of a qualitatively good bearing support and, on the other hand, that it can be exchanged with another with a minimum expenditure of time and labor.
2. Description of the Prior Art
It is known to equip cylinders of this type, particularly cutting and formatting cylinders, with cylindrical bearing journals on both sides, on which anti-friction radial bearings and possibly vacuum air control valves are disposed and secured axially. To ensure that such cylinders run free of play and radial imbalance, pretensioning bearings are arranged on the bearing journals axially beside the main bearings serving to take up the bearing forces. The bearing play of the main bearings is pushed out here by pretensioning forces to one side by means of the pretensioning bearings; see DE-OS No. 27 50 530 and DE-OS No. 29 12 458. The possibility to change cylinders results from the fact that the main bearings of the cylinders are received at divided bearing positions.
Cylinder bearings of this type have economic as well as technical disadvantages. The main bearings and the pretensioning bearings are part of the supply schedule of the cylinders, although the cylinders, being cutting and formatting cylinders, are parts subject to wear. If repairs on a cylinder are required, for instance for regrinding a cutting cylinder, the old main and pretensioning bearings must be pulled off before such reconditioning can begin and must be replaced by new bearings when the work is completed. This increases the cost of reconditioning work considerably. Since the main and pretensioning bearings are arranged axially side by side on the respective cylinder journal on the end face, the cylinder is bent by the pretensioning force which causes a torque by means of the lever arm of the distance from the main and pretensioning bearing. A further disadvantage resides also in that the divided support positions which, first, provide no exact and accurate seating of the cylinder bearings and, second, do not permit a rapid exchange of cylinders. In addition, the overall length of the cylinder is increased since the main and pretensioning bearings as well as usually a vacuum air valve on one side are arranged on their journal at the end face. This is reflected in higher material and manufacturing costs.